JP2004009591A - Reflector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflector having a reflection ratio necessary for back light of brightness and of high reliability and light fastness. <P>SOLUTION: A light diffusion layer (B) is formed on a polymer film (A). When the layer (A), layer (B), an underlying layer (C), a reflective layer (D) mainly containing silver, and a protective layer (E) are laminated in turn, (1) the reflective layer (D) is subjected to vacuum vapor deposition under a pressure of 13.3 mPa or below, or (2) the layer (D) is subjected to spatter deposition under a pressure of 20 mPs or below, preferably 7-0.1 mPa, to obtain the reflector. The obtained reflector is installed on the lower surface of the photo-conductive board of the back light with its reflecting surface turned upward. <P>COPYRIGHT: (C)2004,JPO

Description

【００３３】
【発明の効果】
本発明の反射体は、高反射率を示すと共に、硫化水素暴露試験に対する耐性を有し、バックライトの導光板の下面に設置することで、従来に比べ高い輝度を安定に得られることから、液晶の表示能力を向上させることができるため、本発明の工業的意義は大きい。
【図面の簡単な説明】
【図１】本発明における反射体の一例を示す断面図
【図２】本発明の光源装置の一例
【符号の説明】
１０　高分子フィルム（Ａ）
２０　光拡散層（Ｂ）
３０　下地層（Ｃ）
４０　銀反射層（Ｄ）
５０　保護層（Ｅ）
６０　冷陰極管
７０　ランプリフレクター
８０　導光板
９０　反射体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reflector in which a metal mainly composed of silver is laminated on a polymer film, and further to a sidelight type backlight device applied to a liquid crystal display device and the like using the same.
[0002]
[Prior art]
Compared to conventional CRT displays, liquid crystal displays are thinner, lighter and smaller, operate at lower voltages, consume less power and can be more energy efficient. It is widely used as displays for small and medium-sized equipment, monitors for video cameras, digital cameras, and the like.
[0003]
Since the liquid crystal itself does not emit light, the use of external light or a lighting device is required for use as a display device. There are various forms depending on the purpose of use of the display device, but recently, a side light that uses a LED as a point light source or a cold cathode tube as a line light source as a light source and converts it into a uniform surface light source using a light guide plate. (Or edge light) type backlights have become mainstream.
[0004]
In such a device, a diffuse reflection member made of a white PET film or the like is often arranged below the light guide plate, and uniform brightness can be obtained by diffusing light by the reflector. However, these diffusely reflecting members have almost no regular reflection component and are therefore uniform as a whole, but do not provide sufficient luminance. In addition, in a reflection sheet in which aluminum is laminated on a transparent PET film, although the luminance is higher than that of white PET, slight distortion of the sheet greatly affects luminance unevenness because there is no diffuse reflection component, so that uniform luminance can be obtained. Can not.
[0005]
The present inventors have developed a reflector under a light guide plate in which a reflective layer mainly composed of silver is laminated on a polymer film having a special surface shape in order to obtain a backlight having high luminance and uniform luminance.
However, silver has a property of blackening by reacting with sulfur or ozone in the environment, and it is necessary to provide a transparent protective layer on the outermost surface to maintain practical luminance.
[0006]
As the protective layer, a transparent oxide such as SiO ₂ , TiO ₂ , ZnO, or ITO, or a thin layer of various polymers can be used, and the adhesion between the silver layer and the protective layer and the sufficient protective ability can be used. However, there is a problem that a change in chromaticity due to absorption by the protective layer cannot be ignored in a film thickness exhibiting the following. Therefore, in addition to the examination of the protective layer, a measure for suppressing the reaction between silver and sulfur / ozone is required.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a reflector comprising a reflective layer mainly composed of silver, which has improved resistance to exposure to hydrogen sulfide.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to solve the above-described problems, and as a result, have found that it is possible to improve the resistance to hydrogen sulfide exposure by controlling the lamination conditions of the silver reflective layer.
[0009]
That is, the present invention
(1) A reflector characterized in that a reflective layer mainly composed of silver is vacuum-deposited under a pressure of 13.3 mPa or less.
(2) A reflector characterized in that a reflection layer mainly composed of silver is sputter-deposited at a pressure of 20 mPa or less.
(3) The reflector according to (1) or (2), wherein the total reflectance at 550 nm is 90% or more and the diffuse reflectance is 50% or less.
(4) A sidelight-type backlight comprising the reflector according to any one of (1) to (3) below a light guide plate.
About.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The polymer film used in the substrate used for the reflector of the present invention includes, for example, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonates such as bisphenol A-based polycarbonate, polyethylene, polypropylene and the like. Polyolefins, cellulose derivatives such as cellulose triacetate, vinyl resins such as polyvinylidene chloride, polyimides, polyamides, polyethersulfone, polysulfone resins, polyarylate resins, and films made of various plastics such as fluorine resins. However, the material is not necessarily limited to these, and any material having a high glass transition point to some extent and having a smooth surface can be used. Among them, polyethylene terephthalate is preferred.
[0011]
The thickness of the polymer film to be used requires a certain degree of stiffness in the sheet, and it is usually desirable that the thickness be 100 to 200 μm.
The reflector of the present invention can be obtained by, for example, constructing a special surface shape on the above-mentioned polymer film, and then laminating an underlayer, a reflective layer mainly composed of silver, and a surface protective layer.
The above-mentioned special surface shape means that a reflection layer mainly composed of silver is formed on a smooth surface by forming 1 to 100 protrusions having a height of about 20 μm to 30 μm per square mm. This is a surface shape constructed so that the diffuse reflectance becomes 1 to 50% when formed.
[0012]
The special surface shape is constructed by a method described below. That is, when formed by applying particles, organic particles such as polyester, acrylic, polystyrene, and vinylbenzene, inorganic fine particles such as silica, alumina, titania, and zirconia, tin oxide, indium oxide, cadmium oxide, and oxide Conductive fine particles such as antimony can also be used. Although not necessarily limited to these, acrylic resin is particularly preferably used.
[0013]
When the surface shape is formed by printing, screen printing using an ultraviolet (UV) curable ink is preferably used. The screen printing method is capable of printing as long as it is an ink-like material other than the printing ink, and it is also possible to print ink having a thickness of 10 μm to 30 μm, which is 5 to 10 times that of offset printing or the like, It is suitable for constructing a special surface shape in the present invention.
[0014]
The method for constructing the special surface shape is not limited to the above-described particle coating method or printing method, but may be a method in which a resin film is pressed against an uneven mold.
[0015]
The back surface of the polymer film (A) used in the present invention is desirably subjected to easy lubrication for the purpose of improving workability when assembling as a liquid crystal backlight module. The lubricating treatment can be easily achieved by coating a lubricating particle or using a polymer film matted by a sand blast method or other methods. The effect of the present invention does not depend on the presence or absence of the slippery treatment on the back surface.
The reflector of the present invention can be obtained, for example, by forming a reflective layer on a polymer film having a special surface shape as described above. The reflective layer is preferably a base layer (C), a reflective layer (D) mainly composed of silver, and a protective layer (E) in order from the polymer film having a special shape, that is, the light diffusion layer (B).
[0016]
The underlayer (C) is made of a single metal such as gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, palladium, or an alloy composed of two or more kinds, or aluminum oxide. Is preferably used, zinc oxide doped with 5% by weight or less, zinc oxide doped with 10% by weight or less of gallium, oxide of indium and tin (ITO), or transparent oxide such as silicon dioxide.
For the reflective layer (D) mainly composed of silver, a simple substance of silver or an alloy mainly composed of silver with copper, palladium, platinum or neodymium is preferably used. It is preferable that the purity of silver or an alloy mainly composed of silver is 100%. However, gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, Indium, manganese, titanium, palladium and the like may be contained as impurities.
(D) The protective layer is made of a single metal such as gold, copper, nickel, iron, cobalt, tungsten, molybdenum, tantalum, chromium, indium, manganese, titanium, palladium, or an alloy composed of two or more kinds, or aluminum oxide. Transparent oxides such as zinc oxide doped with 5% by weight or less, zinc oxide doped with 10% by weight or less of gallium, indium and tin oxide (ITO), and silicon dioxide are preferably used.
[0017]
The method of forming the metal thin film layer includes a wet method and a dry method. The wet method is a general term for the plating method, and is a method of depositing a metal from a solution to form a film. A specific example is a silver mirror reaction. On the other hand, the dry method is a general term for a vacuum film forming method, and specific examples thereof include a resistance heating vacuum evaporation method, an electron beam heating vacuum evaporation method, an ion plating method, and an ion beam assisted vacuum evaporation method. And a sputtering method. In particular, a vacuum film forming method capable of a roll-to-roll method for continuously forming a film is preferably used in the present invention.
[0018]
The thickness of each layer in the reflection layer of the present invention is preferably as follows.
The thickness of the underlayer (C) is preferably 1 to 20 nm, more preferably 5 to 10 nm. When the thickness of such a layer is less than 1 nm, a desired barrier effect cannot be obtained, and the reflection layer (D) mainly composed of silver is aggregated to lower the reflectance, which is not preferable. Even if the thickness is more than 400 nm, there is no change in the effect.
The thickness of the reflection layer (D) mainly composed of silver is preferably from 70 to 400 nm, more preferably from 100 to 300 nm, and still more preferably from 120 to 250 nm. If the thickness of such a layer is smaller than 70 nm, a desired reflectance may not be obtained because a sufficient reflective layer is not formed. Even if the thickness is more than 400 nm, the effect does not change.
When a metal layer is used, the thickness of the protective layer (E) is preferably from 5 to 50 nm, more preferably from 5 to 30 nm. When a transparent oxide is used, the thickness is preferably 1 to 20 nm, more preferably 5 to 10 nm. If the respective film thicknesses are too thin, the desired effect cannot be obtained, and if the thicknesses are too large, the characteristics of the reflective layer (D) mainly composed of silver are hindered, which may be undesirable.
[0019]
The identification of the polymer film (A) can be easily confirmed by infrared spectroscopy. If the back surface has not been subjected to the slippery treatment, the back surface may be directly measured by the ATR method in some cases. When the back surface has been subjected to the slippery treatment, it can be easily confirmed by peeling the treatment layer on the front surface side or the back surface side with a solvent or measuring the substrate after mechanically peeling off.
[0020]
The shape of the light diffusion layer (B) can be easily confirmed with various optical microscopes, electron microscopes, stylus roughness meters, and the like.
The above-mentioned total reflectance and diffuse reflectance can be easily measured by a self-recording spectrophotometer in the ultraviolet / visible region using an integrating sphere.
Regarding the composition of each of the underlayer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E), X-ray fluorescence analysis, X-ray photoelectron spectroscopy, Auger spectroscopy, secondary ion mass Measurement can be easily performed by using an analysis method or the like. The composition of each layer can be easily confirmed by measuring the so-called depth profile by X-ray photoelectron spectroscopy, Auger spectroscopy, secondary ion mass spectrometry, or the like.
[0021]
As a method of measuring the film thickness of each layer, there is a method using a stylus roughness meter, a repetitive reflection interferometer, a microbalance, a quartz oscillator method, and the like, and in particular, the quartz oscillator method can be measured during film formation. Therefore, it is suitable for obtaining a desired film thickness. There is also a method in which the conditions for film formation are determined in advance, a film is formed on a sample substrate, the relationship between the film formation time and the film thickness is examined, and the film thickness is controlled by the film formation time.
When the reflectance of the reflector formed as described above is measured from the reflection layer side, it is usually 90 to 95% at a wavelength of 550 nm.
The weather resistance in the present invention is the ability to maintain the reflectance to hydrogen sulfide exposure evaluated by the method described below. That is, a sample cut into a 5 cm square is placed in a sealed container, and hydrogen sulfide is introduced so as to have a concentration of 30 ppm. Hydrogen sulfide is heavy and tends to settle to the lower part, and the mixing due to diffusion seen with light gases is not always sufficient. Therefore, a device for sufficiently diffusing hydrogen sulfide is required, and for example, it can be performed by the method described below. That is, two cocks are provided in advance in a sealed container to be used, and a bag-shaped one such as a syringe and a Tedlar bag to which the capacity is changed without resistance and which does not allow gas to permeate is mounted. By moving the piston of the syringe back and forth with the cock open, gas is moved into the container, the introduced hydrogen sulfide is agitated and diffused, and then the cock is closed and the syringe and the bag may be removed. A sample is taken out after 24 hours at room temperature in that state, and the reflectance is measured.
If the resistance to hydrogen sulfide exposure is sufficient, the reflectance before the exposure test is maintained, but if the resistance is insufficient, blackening is observed even with the naked eye due to the formation of silver sulfide, and the reflectance depends on the degree of blackening. descend.
[0022]
The surface light source device of the present invention is characterized in that the reflector manufactured as described above is installed on the lower surface of the light guide plate with the reflective layer side as the upper surface. The surface light source device is generally used as a side light type, and does not have any problem.
The material of the light guide plate used is, for example, an acrylic resin such as polymethyl methacrylate, a polycarbonate resin such as a polycarbonate or a polycarbonate / polystyrene composition, a transparent resin such as an epoxy resin, or a wavelength of 400 to 700 nm such as glass. Materials showing transparency in the region are preferably used, but the materials are not necessarily limited to these materials as long as they are transparent according to the wavelength region of the light source. The thickness of the light guide plate can be appropriately determined depending on the purpose of use, the size of the light source, and the like.
As a form of the light guide plate used, a dot print type light guide plate or a prism type light guide plate is used, and a combination with a prism type light guide plate is more preferably used. In combination with the prism type light guide plate, a front prism type light guide plate may be used at all, but a combination with a back side prism type light guide plate is more preferably used because higher luminance is easily obtained.
[0023]
Examples of the light source to be used include an incandescent light bulb, a light emitting diode (LED), an electroluminescence (EL), a fluorescent lamp, a metal halide lamp, and the like, and among them, a fluorescent lamp is preferably used. Fluorescent lamps are classified into a hot cathode type and a cold cathode type. The hot cathode type has a high luminous efficiency, but the cold cathode type is superior in terms of life, so the cold cathode type is preferably used.
[0024]
As described above, in the present invention, on the light-scattering layer (B) provided on the polymer film (A), the underlayer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E ) Is formed by vacuum-depositing (1) a reflective layer (D) mainly composed of silver under a pressure of 13.3 mPa or less, or (2) a reflective layer (D) mainly composed of silver. By sputtering at 20 mPa or less, preferably 0.1 mPa to 7 mPa, it is possible to obtain a reflector having excellent reflectivity and excellent resistance to exposure to hydrogen sulfide. By incorporating the reflector as a reflector of a backlight, a backlight having high luminance and high durability can be obtained.
【Example】
Hereinafter, the present invention will be specifically described with reference to examples.
[0025]
(Example 1)
A solution in which an acrylic particle having an average particle diameter of 30 μm, an acrylic resin as a binder, and a solvent composed of toluene and methyl ethyl ketone are used. The solid content ratio is 35%, and the ratio of particles in the solid content is 10.0% by weight. Was prepared and applied onto a 188 μm-thick PET film to obtain a light diffusion layer (B).
Next, on the light diffusion layer (B), zinc oxide (purity of 99.9% or more) doped with 2% of aluminum oxide at a degree of vacuum of 7 mPa using an electron beam heating vacuum evaporation method was applied. Was set to 5 nm.
Subsequently, without removing the sample from the vacuum apparatus, silver (purity of 99.9% or more) was mainly formed by using an electron beam heating vacuum evaporation method at a degree of vacuum of 7 mPa so that the film thickness became 120 nm. The reflection layer (D) was laminated.
Subsequently, without removing the sample from the vacuum apparatus, zinc oxide (purity of 99.9% or more) doped with 2% of aluminum oxide at a degree of vacuum of 7 mPa using an electron beam heating vacuum evaporation method was used. The protective layer (E) was laminated so as to have a thickness of 5 nm.
The obtained reflector was set on a Hitachi self-recording spectrophotometer (model U-3400) with an integrating sphere of 150φ, and the total reflectance measured from the reflection layer side at 550 nm was 92.4%. The reflector after the measurement was placed in a sealed container, hydrogen sulfide gas was introduced to a concentration of 30 ppm, and the mixture was sufficiently mixed, and then left at room temperature for 24 hours. The total reflectance after the hydrogen sulfide exposure test was 92.2%. No particular change was observed by visual observation. Table 1 shows the results.
[0026]
(Example 2)
A reflector was laminated in the same manner as in Example 1 except that the degree of vacuum when depositing the base layer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E) was 10 mPa.
The total reflectance of the obtained reflector was measured according to Example 1. The total reflectance at 550 nm was 92.6% before the hydrogen sulfide exposure test and 92.5% after the exposure test. No particular change was observed by visual observation. Table 1 shows the results.
[0027]
(Comparative Example 1)
A reflector was laminated in the same manner as in Example 1 except that the degree of vacuum when depositing the base layer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E) was 15 mPa.
The total reflectance of the obtained reflector was measured according to Example 1. The total reflectance at 550 nm was 92.3% before the hydrogen sulfide exposure test and 88.8% after the exposure test. No noticeable difference was observed by visual observation. Table 1 shows the results.
[0028]
(Comparative Example 2)
A reflector was laminated in the same manner as in Example 1 except that the degree of vacuum when depositing the underlayer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E) was 20 mPa.
The total reflectance of the obtained reflector was measured according to Example 1. The total reflectance at 550 nm was 92.1% before the hydrogen sulfide exposure test and 74.9% after the exposure test. The occurrence of black spots was slightly observed by visual observation. Table 1 shows the results.
[0029]
(Example 3)
A light diffusing layer (B) was obtained according to Example 1.
Next, on the light diffusion layer (B), zinc oxide (purity of 99.9% or more) doped with 2% of aluminum oxide by DC magnetron sputtering at a degree of vacuum of 5 mPa was used as a target, and the purity was 99.5. % Or more of argon gas was used as a sputtering gas, and the underlayer (C) was laminated so as to have a thickness of 5 nm.
Subsequently, without removing this sample from the vacuum apparatus, a film was formed at a degree of vacuum of 5 mPa by a DC magnetron sputtering method using silver (purity of 99.9% or more) as a target and argon having a purity of 99.5% or more as a sputtering gas. A reflective layer (D) mainly composed of silver was laminated so as to have a thickness of 120 nm.
Subsequently, without removing the sample from the vacuum apparatus, zinc oxide (purity of 99.9% or more) doped with 2% of aluminum oxide by DC magnetron sputtering at a degree of vacuum of 5 mPa was used as a target, and the purity was 99.5%. Using the above argon as a sputtering gas, a protective layer (E) was laminated so that the film thickness became 5 nm.
The total reflectance of the obtained reflector was measured according to Example 1. The total reflectance at 550 nm was 93.4% before the hydrogen sulfide exposure test and 93.0% after the exposure test. No particular change was observed by visual observation. Table 1 shows the results.
[0030]
(Example 4)
A reflector was laminated in the same manner as in Example 1 except that the degree of vacuum at the time of sputtering the underlayer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E) was 10 mPa.
The total reflectance of the obtained reflector was measured according to Example 1. The total reflectance at 550 nm was 93.6% before the hydrogen sulfide exposure test and 93.4% after the exposure test. No particular change was observed by visual observation. Table 1 shows the results.
[0031]
(Example 5)
A reflector was laminated in the same manner as in Example 1 except that the degree of vacuum when sputtering the underlayer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E) was set to 20 mPa.
The total reflectance of the obtained reflector was measured according to Example 1. The total reflectance at 550 nm was 92.8% before the hydrogen sulfide exposure test and 91.7% after the exposure test. No particular change was observed by visual observation. Table 1 shows the results.
[0032]
(Comparative Example 3)
A reflector was laminated in the same manner as in Example 1 except that the degree of vacuum at the time of sputtering the underlayer (C), the reflective layer (D) mainly composed of silver, and the protective layer (E) was 30 mPa.
The total reflectance of the obtained reflector was measured according to Example 1. The total reflectance at 550 nm was 93.3% before the hydrogen sulfide exposure test and 84.2% after the exposure test. Observation with the naked eye revealed minute black spots. Table 1 shows the results.
[Table 1]

[0033]
【The invention's effect】
The reflector of the present invention exhibits a high reflectance, has resistance to the hydrogen sulfide exposure test, and can be stably provided with a higher luminance than before by being installed on the lower surface of the light guide plate of the backlight. Since the display capability of the liquid crystal can be improved, the present invention has great industrial significance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example of a reflector according to the present invention. FIG. 2 is an example of a light source device according to the present invention.
10 Polymer film (A)
20 Light diffusion layer (B)
30 Underlayer (C)
40 silver reflective layer (D)
50 Protective layer (E)
Reference Signs List 60 cold cathode tube 70 lamp reflector 80 light guide plate 90 reflector

Claims (4)

On at least the polymer film (A), a light diffusion layer (B), an underlayer (C), a reflective layer (D) mainly composed of silver, and a protective layer (E) are formed of A / B / C / D / E. A reflector constituted in this order, wherein the reflector mainly composed of silver is vacuum-deposited under a pressure of 13.3 mPa or less. On at least the polymer film (A), a light diffusion layer (B), an underlayer (C), a reflective layer (D) mainly composed of silver, and a protective layer (E) are formed of A / B / C / D / E. A reflector constituted in this order, wherein a reflection layer mainly composed of silver is sputter-deposited at a pressure of 20 mPa or less. 3. The reflector according to claim 1, wherein the total reflectance at 550 nm is 90% or more and the diffuse reflectance is 50% or less. A sidelight type backlight device comprising the reflector according to claim 1 installed below a light guide plate.

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